Cephalosporins antibiotics: what they are and how they work

Cephalosporins are a common class of antibiotics your doctor may prescribe for many bacterial infections. They kill or stop bacteria from growing by interfering with the cell wall. You’ll see them used in clinics and hospitals because they cover a wide range of bugs and come in oral and IV forms.

Which infections do cephalosporins treat?

These drugs treat respiratory infections, ear infections, skin and soft tissue infections, urinary tract infections, and certain bone and blood infections. Stronger, later-generation cephalosporins (like ceftriaxone or cefepime) are used for severe infections such as meningitis or sepsis. Common names you’ll hear: cephalexin (oral), cefuroxime, cefdinir, ceftriaxone (IV), and cefepime (IV).

Doctors choose a specific cephalosporin based on the likely bacteria and how sick the patient is. For example, cephalexin often treats uncomplicated skin infections at home. Ceftriaxone is used in the ER for suspected serious infections because it works fast and is given by injection.

Safety tips and common side effects

Most people tolerate cephalosporins well. The usual side effects are mild: stomach upset, diarrhea, and sometimes yeast infections. A serious allergic reaction (anaphylaxis) is rare but requires immediate care—look out for rash, swelling, trouble breathing, or dizziness.

If you have a penicillin allergy, tell your provider. Cross-reaction is less common than once thought, but caution is needed if your allergy was severe. People with kidney problems may need dose changes. Some cephalosporins can affect blood clotting if you take warfarin, so your INR may need checking.

Never mix certain cephalosporins with alcohol advice without asking your pharmacist. Also, ceftriaxone should not be mixed with IV calcium solutions in newborns because of rare but serious risks. Pregnant or breastfeeding? Most cephalosporins are considered safe, but confirm with your clinician.

Finish the full course unless your doctor tells you otherwise. Stopping early can let the infection come back and encourage resistant bacteria. If diarrhea is severe or contains blood, contact your provider—this could signal a Clostridioides difficile infection that needs treatment.

Practical tips: take oral cephalosporins with food if they upset your stomach, store them as directed, and keep a list of your allergies and current medicines for every medical visit. Ask about kidney dosing if you’re older or have chronic kidney disease.

Questions for your prescriber: What bacteria are you treating? Is this the best antibiotic choice? How long will I take it? What side effects should I expect? These quick questions help you get safe, effective care and avoid common problems with antibiotics.